1. Field of the Invention
The present invention relates to a semiconductor device, and more particularly to a semiconductor device supplying a charging current to an element to be charged (hereinafter, also referred to as a charging-target element).
2. Description of the Background Art
A semiconductor device driving a power semiconductor element such as an IGBT (Insulated Gate Bipolar Transistor) has been developed. In such a semiconductor device, for example, a floating circuit is used as a circuit for driving a power semiconductor element which experiences great potential fluctuation. In order to supply a voltage to the floating circuit, for example, a bootstrap scheme has been adopted, in which a capacitor connected to a power supply voltage with a diode being interposed is employed as a power supply (see, for example, Japanese Patent Laying-Open Nos. 06-188372, 2006-005182 and 2004-047937 (Patent Documents 1 to 3) and Kiyoto Watabe et al., “A Half-Bridge Driver IC with Newly Designed High Voltage Diode,” Proceedings of The 13th International Symposium on Power Semiconductor Devices & ICs, ISPSD '01, Jun. 4-7, 2001, Osaka International Convention Center, JAPAN (Non-Patent Document 1)).
According to the configuration described in Patent Documents 1 to 3, however, an n-type diffusion region serving as a path of the charging current from the power supply to the capacitor is narrowed by extension of a depletion layer, and therefore, the charging current becomes smaller.
Meanwhile, Non-Patent Document 1 fails to suggest prevention of power loss caused as a result that holes injected from a p-type diffusion region to an n-type diffusion region, the p-type diffusion region and the n-type diffusion region constituting the diode, flow toward a p− type substrate not toward the capacitor.